Combined Hormonal Contraceptives (CHC)


Please be advised: Our Fact Sheets are currently under review.  If you have any questions about a contraceptive method please contact our Sex Sense Line at 1-800-SEX-SENSE or book an appointment with an Opt clinic. 



(Birth Control Pills/Evra Patch/Vaginal Ring)


What are combined hormonal contraceptives?

Combined hormonal contraceptives (CHCs) use two hormones (estrogen and progestin) to prevent pregnancy from occurring. These hormones are similar to the ones you normally produce in your body.

    How do CHCs work?

    • They prevent pregnancy by stopping ovulation (release of an egg from the ovary) from occurring.

    • They make the mucous of the cervix thick so that it’s hard for sperm to get through into the uterus and they change the lining of the uterus.

    How effective are they?

    Combined hormonal contraceptives are excellent methods of birth control. For typical users, approximately 8 out of every 100 women will experience an accidental pregnancy in the first year. With perfect use, 1 in 100 will become pregnant.


      • Less menstrual cramping and bleeding

      • Predictable, lighter, regular periods

      • Less anaemia caused by iron deficiency

      • Less acne

      • Some protection against non-cancerous breast tumours and ovarian cysts

      • Decreased risk of ovarian and uterine cancer

      • Sexual enjoyment may be enhanced as pregnancy fears are diminished

      • May protect against osteoporosis and endometriosis.


      • You have to remember to take a pill every day, change a patch every week or remove and insert a new vaginal ring monthly.

      • Nausea, vomiting, breast tenderness, headaches or dizziness, and/or spotting are problems women may have the first one to three months

      • Serious complications: potential risks include blood clots, heart attack, stroke, rare liver tumours (these are less common)

      • Risks increase with age and when certain other risk factors are present such as smoking (especially more than 15 cigarettes a day)

      • Possibility of high blood pressure

      • Does not protect against sexually transmitted diseases

      • Certain types may be less effective in women with body weight > 90 kg (198 lb)


      How do I take CHCs?

      • Birth control pills need to be taken at the same time every day to be most effective.

      • The patch needs to be changed every week to be most effective.

      • The vaginal ring needs to be removed after 21 days and a new ring inserted after a 7 day hormone free interval to be most effective.

      • When prescribed, the start date is either the first day of your next period, the Sunday after you begin your period, or use the Quick Start method.

      See our fact sheets:

      Other Considerations

      Some medications interact with the CHCs. If your doctor prescribes any other medications for you, be sure to mention that you are using CHC. There are some antibiotics, seizure medications, and over-the-counter herbal supplements (such as St. John’s Wort), that decrease effectiveness and you may be advised to use a backup method while on these medications.

      There are some serious danger signs that all women using the pill should be aware of. These are:

      A abdominal pain, especially on the right side of your stomach, below your rib cage

      C chest or arm pain, shortness of breath, coughing up blood

      H headaches, severe and not relieved by aspirin or Tylenol

      E eye problems, blurred vision, flashing lights, double vision, blindness

      S swelling, redness, numbness, tingling or pain in the legs

      Seek medical attention immediately if you have any of the above symptoms.














      What if I have sex and don’t use Birth Control?

      Did you know that …for up to 120 hours (5 days)…after sex…you can take emergency pills to avoid becoming pregnant? (The sooner they are taken after an episode of unprotected intercourse the more effective they are)…AND for 7 days…after sex…you can have an IUD put in, so you won’t become pregnant. Not all doctors know about this. If you need to know more or would like the phone numbers of doctors or clinics near you that have emergency birth control, call the SEX SENSE line at 1-800-739-7367 or 604-731-7803 in the lower mainland.

      FS 401
      Revised March 2009